Technical Field
The present disclosure relates to a pneumatic tire tread, and more specifically the present disclosure relates to a pneumatic tire tread with which air column resonance can be reduced by the formation of flexible fences in a tread main groove, and stable water drainage performance can be achieved up to the final stage of wear.
Description of Related Art
Air column resonance in a main groove formed in a tire tread is produced as a result of resonance (sympathetic vibration) inside a tube (air column) formed by the main groove and the road surface, and the resonant frequency thereof depends on the length of the air column formed between the main groove and the road surface.
This air column resonance sound manifests itself in the form of noise inside and outside the vehicle, and its peak is often at around 1 kHz, which readily reaches the human ear. According to known technology for reducing the air column resonance in a main groove, the air column resonance is reduced by obstructing the flow of air in the direction in which the main groove is formed, by providing members extending from the walls or bottom of the main groove in order to obstruct all or most of the groove. However, by providing this kind of member to obstruct the flow of air in the direction in which the main groove is formed, the flow of water penetrating into the main groove is also obstructed inside the main groove when the vehicle is travelling over a wet road surface and there is a reduction in the water drainage properties between the pneumatic tire and the road surface, so handling stability on a wet road surface is reduced.
In order to deal with this kind of problem in the prior art, FIG. 3 in Patent Document 1 shows technology which achieves both water drainage properties and reduced air column resonance by virtue of the fact that dividing walls 30 (flexible fences) extending from the bottom inside the main groove are disposed in such a way that the greater part thereof, starting from the main groove opening, does not come into contact with the groove walls.
Furthermore, FIG. 7 in Patent Document 2 shows technology which achieves both water drainage properties and reduced air column resonance by virtue of the fact that thin films 4 (flexible fences) extending from the bottom of the main groove are disposed in such a way as to lie at a maximum angle of 30° with respect to a line perpendicular to the groove bottom.